Re: Epoxy Resin Stability Question

From: Guy Allen Brady (galbrady@engin.umich.edu)
Date: Fri Oct 04 1996 - 07:00:26 EEST


Kamesh Tata wrote:
>
> Bronson Hokuf wrote:
>
> Hello;
> 2 weeks ago Guy Allen Brady posted a question regarding long-term,
> ............................................
> Response form the DuPont Somos Solid Imaging Materials Group:
> .........................
> The polymerization will continue within the epoxy resin unless it is
> stopped by a stabilizing inhibitor. The primary indicator of epoxy
> resin instability is a viscosity change, which typically increases
> exponentially with time. Addition of new resin will lower the
> viscosity of unstable vat resin and may provide additional
> stabilizer. However, the new stabilizer may be quickly consumed
> allowing the viscosity to continue to increase. At some time, when
> the vat resin viscosity begins to affect build performance, the resin
> in the vat should be completely replaced and the vat should be
> cleaned.
>
> Bronson R. Hokuf USMail: DuPont Company
> ......................
>
> Bronson,
> Your response to resin stability question is very interesting. Would you please take a few minutes to answer the following question.
>
> Since an increase in viscosity is the primary factor affecting build quality, can we increase resin temperature to bring viscosity down? If yes, how far can we go from resin manufacturer's recommended max. temperature? Any side effects? If this question is too general, could you answer for a specific resin, say, SOMOS 6110 or 7100?
> Kamesh
>
> Kamesh Tata

I'd like a swipe at this.

Viscosity as a function of Temperature goes according to:
        Viscosity(Temp) = A*exp(B/Temp)
where A and B are some constants.

However, increasing the temperature will tend to increase the rate of
the "dark reaction" polymerization. However, the rate of polymerization
as a function of temperature is much more complex and will depend on if
the reaction is diffusion limited (which I doubt). If not, then I'm
sure the DuPont and/or Ciba folks have run some tests to explore this.
Hey, this sounds like someone's Ph.D. thesis....anyone want to own up?
Thomas?

-- 
          G. Allen Brady  --  Graduate Research Assistant          
Materials Science and Engineering - The University of Michigan     
2219 H.H. Dow Bldg.  2300 Hayward Street   Ann Arbor, MI  48105
work: 313/936-0177   fax: 313/747-4807   email:
galbrady@umich.edu          
           http://www-personal.engin.umich.edu/~galbrady



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